Apparatus and method for rapid spectrophotometric pre-test screen of specimen for a blood analyzer

ABSTRACT

A method and apparatus for use in respect of samples which are assessed for quality prior to testing in a clinical analyzer. The method and apparatus identify parameters such as gel level and height of fluid above the gel in blood samples, where appropriate, for the purposes of positioning the specimen for determination of interferents. Such interferents include hemoglobin (Hb), total bilirubin and lipids. These interferents are determined by measurement of absorption of different wavelengths of light in serum or plasma, or other speciments, which are then compared with values obtained through calibration using reference measurements for the respective interferents in serum or plasma or other type of specimen. Determination of temperature of the specimen, as well as specimen type, for example whether the specimen is urine or plasma or serum, may also be carried out.

RELATED APPLICATION INFORMATION

[0001] This is a divisional application of U.S. patent application Ser.No. 09/068,835 filed Feb. 8, 1999.

TECHNICAL FIELD

[0002] This invention relates to spectrophotometry and thespectrophotometric analysis of blood samples. In particular, thisinvention relates to a method and apparatus for providing a rapidpre-test determination of interferent concentration, specimen type andphysical properties of a blood sample for a blood analyzer bymeasurement of absorbance or reflectance.

BACKGROUND ART

[0003] Clinical laboratory tests are routinely performed on the serum orplasma of whole blood. In a routine assay, red blood cells are separatedfrom plasma by centrifugation, or red blood cells and various plasmaproteins are separated from serum by clotting prior to centrifugation.

[0004] Haemoglobin (Hb), bilirubin (Bili) and light-scatteringsubstances like lipid particles are typical substances which willinterfere with, and affect spectrophotometric and other blood analyticalmeasurements. Such substances are referred to as interferents.

[0005] Many tests conducted on plasma or serum samples employ a seriesof reactions which terminate after the generation of chromophores whichfacilitate detection by spectrophotometric measurements at one or twowavelengths. Measurement of interfering substances prior to conductingsuch tests is important in providing meaningful and accurate testresults. In fact if a sample is sufficiently contaminated withinterferents, tests are normally not conducted as the results will notbe reliable.

[0006] In analytical laboratories bar codes are increasingly being usedto identify samples, and such laboratories routinely analyze a varietyof biologic fluids, for example, the most common being blood and urine.

[0007] Specimen integrity directly affects the accuracy of test results.Numerous factors can compromise specimen integrity such as, having theright sample, e.g., blood rather than urine; in the case of a bloodsample, whether it is serum or plasma; the presence of interferents in aplasma or serum sample; the volume of the sample; the sampletemperature; and the location of the upper surface of a gel barrier,which is also referred to herein as the gel level, in a blood sample,where the gel is an inert material used to separate serum or plasma fromclotted or packed blood bells, respectively. Finally, it is criticalthat the sample tested be properly matched to the results of anyassessments on the sample.

[0008] Current methods used for quality assurance and specimen integrityrely principally on visual inspection of the specimen with or withoutcomparison to a reference chart, depending upon which variable is beingassessed. Visual inspection of samples is sometimes employed on aretrospective basis where there is disagreement between test results andclinical status of the patient in order to help explain suchdiscrepancies.

[0009] A sample of plasma or serum is normally transferred from theoriginal tube to a secondary tube. These secondary tubes may be ambercoloured to protect photo sensitive constituents. Amber colouring makesvisual inspection virtually impossible. On occasion, labels coverportions of the tube further restricting a full visual examination.Further, it is sometimes difficult to distinguish between urine andplasma or serum samples, even in transparent tubes.

[0010] Pre-test screening of specimens by visual inspection issemi-quantitative at best, and highly subjective and may not provide thequality assurance required.

[0011] Furthermore, visual inspection of specimens is a time consuming,rate limiting process. Consequently, state-of-the-art blood analyzers infully and semi-automated laboratories do not employ visual inspection ofspecimens. However, other methods such as direct sampling are not rapidenough or cost effective. In order to obtain a measurement of the sampleof the plasma or serum, specimen tubes must be uncapped, a direct sampleof the specimen taken and diluted prior to measurement.

SUMMARY OF INVENTION

[0012] The disadvantages of the prior art may be overcome by providing arapid and accurate method and apparatus for monitoring blood specimensbefore samples are presented for analysis.

[0013] In one aspect of the invention, the bar code on the specimen tubeis read to identify the specimen, as well as the bar code reading,determination of the gel level of the specimen and the height of fluidabove the gel provide the basis for positioning the specimen containerso that spectral data can be obtained. The spectral data is used in anovel way to determine if the specimen which is presented for analysiscontains interferents and if so, to what extent; to determine specimentype, for example if it is urine or plasma or serum; and to determinethe temperature of the specimen.

[0014] In another aspect of the invention, there is provided anapparatus which incorporates: A. a device to read any bar code presenton a specimen container and thereby identify and provide informationwith respect to positioning the specimen; B. a device to determine thelocation of the upper surface of a gel barrier of the specimen and theheight of fluid above the gel; and C. A spectrophotometric device toirradiate and measure radiation from the specimen so as to determine ifthe specimen which is presented for analysis contains interferents andif so, to what extent; to determine specimen type; and to determine thetemperature of the specimen. This apparatus is capable of thesedeterminations where the sample tube containing the specimen has asample identification label on the exterior surface.

[0015] In a further aspect of the invention, there is provided a methodfor the following: to read any bar code present on specimen containerand thereby identify and provide information with respect to positioningthe specimen; to determine the location of the upper surface of a gelbarrier of the specimen and the height of fluid above the gel; todetermine if the specimen which is presented for analysis containsinterferents and if so, to what extent; to determine specimen type; andto determine the temperature of the specimen. The method of thisinvention allows for these determinations where the sample tubecontaining the specimen has a sample identification label on theexterior surface.

[0016] In yet another aspect of the invention, there is provided anapparatus and a method for the determinations described herein where theradiation from the spectrophotometer, or other appropriate source, istransmitted through the label, container and specimen.

[0017] In one embodiment, the bar code reading as well as the gel leveland height of fluid above the gel are first determined. Thisdetermination provides information essential for proper positioning ofthe sample for the following determinations. The concentration ofinterferents such as hemoglobin (Hb), total bilirubin (calibrated forunconjugated bilirubin, conjugated bilirubin, delta bilirubin, the sumof results for these three gives total bilirubin) and lipids aredetermined by measurement of absorption of different wavelengths oflight in serum or plasma specimens which are then compared with valuesobtained through calibration using reference measurements for therespective interferents in serum or plasma specimens. This is true alsofor determination of temperature of the sample. A determination ofspecimen type, for example whether the specimen is urine or plasma orserum, is also made. This determination is made by recordal of spectraldata for different samples then through statistical analysis, thespectra are classified according to sample type. In addition a bar codereading is carried out either simultaneously, before or after thedetermination of the other parameters. To those skilled in the art, itis clear that although certain sequences of determinations are outlinedhere, any combination or sequence of combinations is within the scope ofthis invention.

[0018] In another embodiment, the bar code reading as well as the gellevel and height of fluid above the gel are first determined. Thisdetermination provides information essential for proper positioning ofthe sample for the following determinations. The concentration ofinterferents such as hemoglobin (Hb), total bilirubin (calibrated forunconjugated bilirubin, conjugated bilirubin, and delta bilirubin, thesum of results for these three gives total bilirubin) and lipids aredetermined by measurement of reflectance of different wavelengths oflight in serum or plasma specimens which are then compared with valuesobtained through calibration using reference measurements for therespective interferents in serum or plasma specimens. This is true alsofor determination of temperature of the sample. A determination ofspecimen type, for example whether the specimen is urine or plasma orserum, is also made. This determination is made by recordal of spectraldata for different samples then through statistical analysis, thespectra are classified according to sample type. In addition a bar codereading is carried out either simultaneously, before or after thedetermination of the other parameters. To those skilled in the art, itis clear that although certain sequences of determinations are outlinedhere, any combination or sequence of combinations is within the scope ofthis invention.

BRIEF DESCRIPTION OF DRAWINGS

[0019]FIG. 1 is a longitudinal cross-section of a sample holder adaptedfor use with LED and radiation source.

[0020]FIG. 2 is a top view of the complete sample holder of FIG. 1.

[0021]FIG. 3 is a longitudinal cross-section of a sample holder adaptedfor use with a laser and radiation source.

[0022]FIG. 4 is a top view of the complete sample holder of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0023] In operation, the apparatus first conducts a determination of thebar code and its position on the tube, and, based on the latterdetermination the tube is presented to the specimen holder 2 in aposition so that the bar code does not interfere with the measurementprocess.

[0024] With respect to measuring gel level and height of fluid 26 abovethe gel 24, the specimen is placed in a specimen holder 2 of FIG. 1,which will also contain a linear array of LEDs 16 on one side of thetube, and a corresponding array of silicon detectors 20 on the oppositeside of the tube. The LEDs 16 are coupled by electrical connections 6 toan electronic driver 4. The detectors 20 are coupled by electricalconnections 7 to a microprocessor (not shown) which analyzes output. Thenumber of LEDs and detectors will depend on the length of the tube,e.g., for a commonly used tube of length 10 cm, 22 LEDs and 20 detectorsarranged 5 mm apart will be necessary to accommodate from a completelyfilled tube to an empty tube. In operation the first detector at the topof the column monitors as the three LED's opposite are flashed insuccession: one which is directly opposite, one 5 mm above, and one 5 mmbelow. The measured distance between the LEDs and the detectors is usedto determine tube diameter. This measurement is performedelectronically, mechanically or optically, or in any combination ofthese. In a preferred embodiment this measurement is performed by acombination of mechanical and electronic operations. The fluid volume iscalculated from the measured tube diameter and the measured height offluid above the gel barrier.

[0025] Alternatively, with respect to measuring gel level and height offluid, a diode laser provides the radiation source wherein the source isfocussed through a series of lenses 30 to spread the radiation 32 acrossthe length of the sample tube. The light being transmitted through thesample tube is passed through a further series of lenses 34 and directedonto a PDA sensor 36. Again, through this apparatus the tube is analyzedin 1 mm increments and the results are correlated to liquid height 26and gel level 24. It is readily apparent that either approach alsoallows for the determination of the hematocrit of any blood sample. Thisis achieved by centrifuging a whole blood sample in a container into twophases, one being the blood cells and the other being serum or plasma.The container is then scanned by the present invention and the length ofthe container that each of the phases occupies is thereby determined.With this data the ratio of the length amounts of the cellular phase andof the serum or plasma phase is converted to hematocrit value.

[0026] Based upon the results from the above determinations, therelative positions of the tube and the fibre optics can be adjusted soas to optimize the position of the fluid compartment for subsequentdeterminations. Consequently, there is space between the walls of thesample holder 2 and the fibre optics 10 and 14 to allow for suchadjustments.

[0027] With respect to determination of sample type, temperature, aswell as for measurement of interferents, reference is made to FIG. 2.The sample 22 is placed into a specimen holder 2 (see FIG. 1 forlongitudinal view) which is located in a housing (not shown). Aradiation source 8, capable of emitting radiation in a range from about400 nm to 2,500 nm, is optically connected by fibre optics 10 to thesample. In operation where absorbance is measured the light source isdirected through the sample, and the transmitted radiation is detectedby a sensor 12, which is a photo diode array (PDA), that is locatedopposite the source. In operation where reflectance is measured, thedetectors are proximate to the emission source (not shown). In bothcases the detector is optically connected by fibre optics 14, or anyother suitable means. In this apparatus the radiation source is split sothat there is a reference beam which by-passes the sample. The apparatusalso contains a means for correlating a sensor response, from the samplepath relative to a sensor response from the reference path, to aquantity of a known substance in said sample. The housing has a cavityfor receiving a sample and a lid for selectively opening and closing thecavity. The radiation source is for emitting a beam of radiation, andthe sensor is responsive to receipt of radiation.

[0028] While the invention has been particularly shown and describedwith reference to certain embodiments, it will be understood by thoseskilled in the art that various other changes in form and detail may bemade without departing from the spirit and scope of the invention.

We claim:
 1. An apparatus for monitoring a specimen before said specimenis presented for clinical analysis, said apparatus comprised of: a)means for holding a specimen container wherein said means and saidcontainer have a longitudinal axis; b) a first radiation source disposedto direct radiation at said specimen and a first radiation detectordisposed to allow collection of transmitted or reflected radiation fromsaid specimen; c) electrical means to couple said first radiation sourceto an electronic driver; d) electrical means to couple said firstradiation detector to a computing means which analyzes output from saiddetector for determination of at least one parameter about saidspecimen; e) means to position said container in said axis of saidholder based on results from said analysis; f) a second radiationsource; g) means to transmit radiation from said second radiation sourceto said specimen; h) means to spectrophotometrically detect transmittedor reflected radiation from said specimen; and i) means for correlatingsaid detected radiation to determine the concentration of at least oneinterferent in said specimen.
 2. The apparatus of claim 1 wherein saidspecimen is one of the group consisting of blood, serum, plasma orurine.
 3. The apparatus of claim 1 wherein said first radiation sourceis comprised of a linear array of LEDs disposed along one side of saidaxis of said container and said first radiation detector is comprised ofa corresponding array of silicon detectors on the opposite side of thecontainer to collect transmitted radiation and wherein aspectrophotometer provides the second radiation source and detectors. 4.The apparatus of claim 1 further comprising one or more lenses to focussaid radiation from said first radiation source to spread said radiationacross said axis of said container, and further wherein said apparatuscontains one or more further lenses which collect transmitted orreflected radiation from said specimen and direct it to saidspectrophotometric radiation detector.
 5. The apparatus of claim 3 or 4wherein said specimen container contains a sample identification labelon the exterior surface of said container.
 6. The apparatus of claim 3or 4 wherein said first radiation and radiation from saidspectrophotometer is transmitted through a label, a container and aspecimen.
 7. A method for monitoring specimens before said specimens arepresented for clinical analysis comprising the steps of: a) placing aspecimen in a specimen container; b) placing said specimen containerinto a holding means; c) applying radiation from a first radiationsource to said specimen and collecting transmitted or reflectedradiation from said specimen; d) analyzing said collected radiation todetermine at least one parameter about said specimen; and e) based onresults from said one or more determinatioi is, positioning saidcontainer in said holder for further analysis wherein said furtheranalysis comprises the steps of: (i) spectrophotometrically applyingradiation from a second radiation source to said specimen and detectingtransmitted or reflected radiation from said specimen; and (ii)correlating said spectrophotometrically detected radiation to determinethe concentration of at least one interferent in said specimen.
 8. Themethod of claim 7 wherein said container has a longi'Wdinal axis andsaid radiation from said first radiation source is focussed through oneor more lenses to spread said radiation across said axis of saidcontainer, said radiation being transmitted through said container andwherein reflected or transmitted radiation from said container is passedthrough one or more lenses and thereby directed to said radiationdetector.
 9. The method of claim 7 wherein said container has alongitudinal axis and said radiation from said first radiation source isapplied through a linear array of LEDs disposed along on one side ofsaid axis of said container and said transmitted or reflected radiationis collected by a corresponding array of silicon detectors on theopposite side of said container.
 10. The method of claim 8 or 9 whereinsaid specimen is one of the group consisting of blood, serum, plasma orurine.
 11. The method of claim 8 or 9 where said specimen containercontains a sample identification label on the exterior surface of saidcontainer and said radiation from said first and second radiationsources is transmitted through said label, container and specimen. 12.The method of claim 8 or 9 wherein a bar code is present on saidcontainer and said bar code is read to identify said specimen.
 13. Themethod of claim 7 , 8 or 9 wherein the parameter determined is one ormore of the group consisting of a gel level, the thickness of said gel,the height of fluid above said gel, and the volume of fluid above saidgel.
 14. The method of claim 7 , 8 or 9 wherein saidspectrophotometrically detected radiation is used to determine theconcentration of one or more of the group consisting of hemoglobin,total bilirubin, unconjugated bilirubin, conjugated bilirubin, deltabilirubin, biliverdin, and lipid.
 15. The method of claim 14 whereinsaid spectrophotometrically detected radiation is used to determine thetemperature of said specimen.
 16. The method of claim 14 wherein saidspectrophotometrically detected radiation is used to determine the typeof said specimen.
 17. A method for monitoring blood specimens inS'P-ecimen containers before said specimens are presented for clinicalanalysis comprising the steps of: a) reading any bar code on saidcontainer; b) determining the location of a gel level of said specimenand the height of any fluid located above said gel c) on the basis ofsaid determination positioning said container such that spectral datacan be obtained; and d) interpreting said spectral data to determine theconcentration of one or more intereferents, and specimen type andspecimen temperature.
 18. The method of claim 17 wherein saiddeterminations are made when said container has a label on the exteriorsurface of said container and said determinations are made through saidlabel.
 19. The method of claim 17 wherein said interferents are selectedfrom the group consisting of hemoglobin, total bilirubin, unconjugatedbilirubin, conjugated bilirubin, delta bilirubin, biliverdin, and lipid.20. A method of determining the hematocrit of a blood sample comprisingthe steps of: a) centrifuging a whole blood sample in a tube having anaxis, to separate the sample into two phases, one being the blood cellsand the other the serum or plasma; b) while maintaining said phasesseparate, optically scanning the phases in said tube along said tubeaxis to determine a length of said axis that each of said phasesoccupies; c) calculating the ratio of the axis length amounts of thecellular phase and of the serum or plasma phase; and d) converting saidratio to hematocrit value.